QExtSerialPort - receives data only, after port was first opened in other terminal-like application

Hi, i'm rather new to Qt, and started a project which require a serial port connection, so I downloaded the qextserialport library, and compiled It into the project. It properly connects with the device, but there is a problem when It comes to data receiving. When I start the compiled application, and send data from the device It receives only 1 byte which is 7F in hex (device send string: "KeyA pressed").
The problem disappears when I start other app for serial port communication, open port on which the device is connected in that app and close It.
Any ideas what is going on ?
here is my code for opening serial port :
@
serialPort = new QextSerialPort("COM3");
serialPort->setBaudRate(BAUD115200);
serialPort->setDataBits(DATA_8);
serialPort->setParity(PAR_NONE);
serialPort->setFlowControl(FLOW_OFF);
serialPort->setStopBits(STOP_1);
serialPort->setTimeout(500);
serialPort->setQueryMode(QextSerialPort::EventDriven);
serialPort->open(QIODevice::ReadWrite | QIODevice::Unbuffered);

I didn't hear about that library earlier, I will give it a try :)
As I see you are one of the developers of that library, so I have a question - does it support the readyRead() signal ? or do I have to manually handle the way I check if there is any incoming data ?